The Ubuntu 10.04 server has eth0 Internet interface configured by means of an ISP's DHCP.
At the same time the server has static eth0 LAN interface to which it provides masquerading (NAT) and LAN-internal DHCP service (dhcp3-server).

As far as I've understood the manual, I had to hardcode DNS servers to advertise through LAN DHCP with option domain-name-servers in dhcpd.conf.

But what if the ISP changes his DNS server IP silently (we use a SOHO-class ISP, so this won't surprise me much)? Can I configure dhcpd to advertise the DNS server the server uses itself, the one gotten by its DHCP client mechanism?

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2

Not really an answer to your question, but in this kind of setup I have always used dnsmasq to create and easy local dns cache. It also the road that most consumer level routers take, so it's probably quite reasonable. Note that dnsmasq could also double as a dhcp server for small networks.
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Javier RiveraDec 21 '10 at 10:50

This question seems abandoned, there is not further information or activity added to it for several months. I am flagging this to be closed by a moderator. If you think this issue is still affecting you you can flag a moderator to re-open it.
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Bruno PereiraFeb 3 '12 at 0:42